U.S. patent number 7,467,916 [Application Number 11/074,820] was granted by the patent office on 2008-12-23 for semiconductor-manufacturing apparatus equipped with cooling stage and semiconductor-manufacturing method using same.
This patent grant is currently assigned to ASM Japan K.K.. Invention is credited to Takeshi Watanabe, Takayuki Yamagishi.
United States Patent |
7,467,916 |
Yamagishi , et al. |
December 23, 2008 |
**Please see images for:
( Certificate of Correction ) ** |
Semiconductor-manufacturing apparatus equipped with cooling stage
and semiconductor-manufacturing method using same
Abstract
A wafer transfer apparatus includes: (A) a mini environment that
connects to a wafer storage part and a load lock chamber and is
equipped with a transfer robot inside, in order to transfer wafers
between the wafer storage part and load lock chamber in the
presence of air flows; and (B) a cooling stage that opens and
connects to the mini environment from the outside of the mini
environment in the vicinity of the connection port of the load lock
chamber, in order to temporarily hold a wafer so that the wafer is
cooled by the air taken in from the mini environment.
Inventors: |
Yamagishi; Takayuki (Tama,
JP), Watanabe; Takeshi (Tama, JP) |
Assignee: |
ASM Japan K.K. (Tokyo,
JP)
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Family
ID: |
36971124 |
Appl.
No.: |
11/074,820 |
Filed: |
March 8, 2005 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20060204356 A1 |
Sep 14, 2006 |
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Current U.S.
Class: |
414/217;
414/805 |
Current CPC
Class: |
H01L
21/67017 (20130101); H01L 21/67201 (20130101); H01L
21/67778 (20130101) |
Current International
Class: |
B65G
49/07 (20060101) |
Field of
Search: |
;414/217,217.1,935,806,805 ;438/464,782,908 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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10-030183 |
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Feb 1998 |
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JP |
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10-154739 |
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Jun 1998 |
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JP |
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Primary Examiner: Fox; Charles A
Attorney, Agent or Firm: Knobbe, Martens, Olson & Bear
LLP
Claims
What is claimed is:
1. A semiconductor manufacturing apparatus comprising: a reaction
chamber; a transfer chamber connected to said reaction chamber; a
load lock chamber connected to said transfer chamber; a wafer
transfer apparatus comprising: (A) a mini environment which is
defined by walls including a first wall for connecting with an
external wafer storage part and a second wall for connecting with
an external load lock chamber connected to a reaction chamber
opposite the mini environment and which is equipped with a transfer
robot inside, in order to transfer a wafer between said wafer
storage part and said load lock chamber via the mini environment in
the presence of air flows; and (B) a cooling stage having one end
that is connected to the second wall of said mini environment from
the outside of said mini environment in the vicinity of a
connection port thereof for said load lock chamber and that opens
to said mini environment, and another end, opposite to the one end,
that is permanently closed with regard to wafer transfer, in order
to temporarily support a wafer outside the mini environment, the
wafer storage part, and the load lock chamber and guide air to flow
from the mini environment through the cooling stage so that the
wafer is cooled by the air taken in from said mini environment,
wherein the wafer transfer apparatus is capable of transferring a
wafer among said wafer storage part, said load lock chamber, and
said cooling stage by said transfer robot, and the wafer transfer
apparatus is connected to the load lock chamber; and the wafer
storage part connected to said wafer transfer apparatus, wherein
said transfer chamber is positioned below said reaction
chamber.
2. The semiconductor manufacturing apparatus according to claim 1,
wherein said reaction chamber and said load lock chamber are
positioned on an outer periphery of said transfer chamber.
3. A semiconductor manufacturing method that utilizes a wafer
transfer apparatus comprising: (A) a mini environment that connects
a wafer storage part and a load lock chamber and is equipped with a
transfer robot inside, in order to transfer a wafer between said
wafer storage part and said load lock chamber in the presence of
air flows, said load lock chamber being connected to a reaction
chamber opposite the mini environment; and (B) a cooling stage that
opens and is connected to said mini environment from the outside of
said mini environment in the vicinity of a connection port thereof
for said load lock chamber, in order to temporarily hold a wafer so
that the wafer is cooled by the air taken in from said mini
environment, wherein the wafer transfer apparatus is capable of
transferring a wafer among said wafer storage part, said load lock
chamber, and said cooling stage by said transfer robot, said
semiconductor manufacturing method comprising: a) a step of
returning a wafer on which a film has been formed in the reaction
chamber to said load lock chamber; b) a step of transferring said
wafer from said load lock chamber to said mini environment after
said load lock chamber is restored to the atmospheric pressure,
then to said cooling stage by said transfer robot; c) a step of
introducing a next wafer from said wafer storage part to said mini
environment and then to said load lock chamber by said transfer
robot; d) a step of transferring said next wafer from said load
lock chamber to said reaction chamber for formation of film on the
wafer; e) a step of transferring said wafer in said cooling stage
to said mini environment and then to said wafer storage part by
said transfer robot; and f) a step of repeating steps a) through e)
for each subsequent wafer.
4. The manufacturing method according to claim 3, further
comprising a step of blowing air on a wafer surface in said cooling
stage at an air flow rate of at least 1 meter/second.
5. A semiconductor manufacturing method that utilizes a wafer
transfer apparatus comprising: (A) a mini environment that connects
a wafer storage part and a load lock chamber and is equipped with a
transfer robot inside, in order to transfer a wafer between said
wafer storage part and said load lock chamber in the presence of
air flows, said load lock chamber being connected to a reaction
chamber opposite the mini environment; and (B) a cooling stage that
opens and is connected to said mini environment from the outside of
said mini environment in the .vicinity of a connection port thereof
for said load lock chamber, in order to temporarily hold a wafer so
that the wafer is cooled by the air taken in from said mini
environment, wherein the wafer transfer apparatus is capable of
transferring a wafer among said wafer storage part, said load lock
chamber, and said cooling stage by said transfer robot, said wafer
transfer apparatus being capable of storing two wafers in said
cooling stage, said semiconductor manufacturing method comprising:
a) a step of returning a first wafer on which a film has been
formed in the reaction chamber to said load lock chamber; b) a step
of transferring the first wafer from said load lock chamber to said
mini environment after said load lock chamber is restored to the
atmospheric pressure, and then to said cooling stage by said
transfer robot; c) a step of introducing a second wafer from said
wafer storage part to said mini environment and then to said load
lock chamber by said transfer robot; d) a step of transferring said
second wafer from said load lock chamber to said reaction chamber
for formation of film on the wafer; e) a step of returning said
second wafer on which a film has been formed in the reaction
chamber to said load lock chamber; f) a step of transferring said
second wafer from said load lock chamber to said mini environment
after said load lock chamber is restored to the atmospheric
pressure, and then to said cooling stage by said transfer robot; g)
a step of introducing a third wafer from said wafer storage part to
said mini environment and then to said load lock chamber by said
transfer robot; h) a step of transferring said third wafer from
said load lock chamber to said reaction chamber for formation of
film on the wafer; i) a step of transferring said first wafer in
said cooling stage to said mini environment and then to said wafer
storage part by said transfer robot; and j) a step of repeating
steps e) through i) for each subsequent wafer.
6. The manufacturing method according to claim 5, further
comprising a step of blowing air on a wafer surface in said cooling
stage at an air flow rate of at least 1 meter/second.
7. A semiconductor manufacturing method that utilizes a wafer
transfer apparatus comprising: (A) a mini environment that connects
a wafer storage part and a load lock chamber and is equipped with a
transfer robot inside, in order to transfer a wafer between said
wafer storage part and said load lock chamber in the presence of
air flows, said load lock chamber being connected to a reaction
chamber opposite the mini environment; and (B) a cooling stage that
opens and is connected to said mini environment from the outside of
said mini environment in the vicinity of a connection port thereof
for said load lock chamber, in order to temporarily hold a wafer so
that the wafer is cooled by the air taken in from said mini
environment, wherein the wafer transfer apparatus is capable of
transferring a wafer among said wafer storage part, said load lock
chamber, and said cooling stage by said transfer robot, said wafer
transfer apparatus being capable of storing two wafers in said
cooling stage, said semiconductor manufacturing method comprising:
a) a step of introducing an unprocessed wafer from said wafer
storage part to said cooling stage by said transfer robot; b) a
step of returning a processed wafer on which a film has been formed
in the reaction chamber to said load lock chamber; c) a step of
transferring said processed wafer from said load lock chamber to
said mini environment after said load lock chamber is restored to
the atmospheric pressure, and then to said cooling stage by said
transfer robot; d) a step of transferring the unprocessed wafer
from said cooling stage to the mini environment and then to said
load lock chamber by said transfer robot; e) a step of transferring
said unprocessed wafer from said load lock chamber to said reaction
chamber for formation of film on the wafer; f) a step of
introducing a next unprocessed wafer from said wafer storage part
to said cooling stage by said transfer robot; g) a step of
transferring said processed wafer in said cooling stage to the mini
environment and then to said wafer storage part by said transfer
robot; and h) a step of repeating steps b) through g) for each
subsequent wafer.
8. The manufacturing method according to claim 7, further
comprising a step of blowing air on a wafer surface in said cooling
stage at a air flow rate of at least 1 meter/second.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to the structure and utilization
method of a semiconductor manufacturing apparatus of a single wafer
type, which is also a semiconductor manufacturing apparatus of a
vacuum-load-lock type, capable of efficiently processing wafers in
succession.
2. Description of the Related Art
The film formation temperatures in the reaction chambers of general
CVD apparatuses are approx. 400.degree. C. As a result, the wafer
temperature after a backfill of the load lock chamber (a step to
restore the load lock chamber (IOC) to the atmospheric pressure
from a vacuum state via introduction of N.sub.2), which occurs
following film formation, is still high, or around 200.degree. C.
In conventional apparatuses, therefore, wafers must be kept in the
load lock chamber, in a dedicated cooling chamber or in other
location until the hot wafers cool down to temperatures acceptable
to the wafer carrier (approx. 100.degree. C.). This limits the
wafer transfer speed and consequently reduces the throughput.
One measure to address this problem is installing a cooling stage
inside the mini environment that accommodates the transfer robot.
However, it will increase the footprint as a result of a larger
mini environment. Another potential solution is to provide a
separate cooling fan or utilize cooling water in order to promote
the cooling of wafers inside the mini environment. However, this is
a costly approach for obvious reasons.
SUMMARY OF THE INVENTION
The present invention was developed to solve the problems stated
above. In an embodiment, an object is to provide a wafer transfer
apparatus that embodies one or more of the following: low cost,
small footprint, small faceprint, and high throughput.
In an embodiment of the present invention, another object is to
provide a wafer transfer apparatus that embodies high throughput
with a level of stability sufficient for use in the manufacturing
process.
In another embodiment, the present invention provides a
semiconductor manufacturing apparatus equipped with a wafer
transfer apparatus such as those described above.
In yet another embodiment, the present invention provides a method
for manufacturing semiconductors by utilizing a semiconductor
manufacturing apparatus such as those described above.
According to an embodiment of the semiconductor-manufacturing
apparatus which achieves at least one of the objects described
above, the present invention provides a wafer transfer apparatus
comprising: (A) a mini environment that connects to a wafer storage
part and a load lock chamber and is equipped with a transfer robot
inside, in order to transfer a wafer between the wafer storage part
and load lock chamber in the presence of air flows; and (B) a
cooling stage that opens and connects to the mini environment from
the outside of the mini environment in the vicinity of (preferably
above) a connection port thereof for the load lock chamber, in
order to temporarily hold a wafer so that the wafer is cooled by
the air taken in from the mini environment; wherein the wafer
transfer apparatus is capable of transferring a wafer among the
wafer storage part, load lock chamber, and cooling stage by means
of the transfer robot.
The above embodiment further includes at least the following
embodiments:
The wafer transfer apparatus wherein the cooling stage comprises an
air channel and a wafer support that temporarily holds a wafer in
the air channel;
The wafer transfer apparatus wherein a slit is provided at an
outlet of the air channel on a side opposite to an opening that
serves as an inlet of the air channel;
The wafer transfer apparatus wherein an opening of the slit is
adjustable;
The wafer transfer apparatus wherein an opening area of the inlet
of the air channel is larger than an opening area of an outlet of
the air channel;
The wafer transfer apparatus wherein a gate valve is provided at an
opening of an inlet of the air channel;
The wafer transfer apparatus wherein a gate valve is provided at an
outlet of the air channel on a side opposite to an opening that
serves as an inlet of the air channel;
The wafer transfer apparatus wherein the wafer support has a
structure that allows multiple wafers to be stacked on top of one
another at a specified interval;
The wafer transfer apparatus wherein the cooling stage is
positioned on an axis of a connection position on the load lock
chamber so that a wafer can be transferred between the cooling
stage and load lock chamber with the transfer robot without
changing its vertical axis;
The wafer transfer apparatus wherein the mini environment is
equipped, below the transfer robot, with a damper with an
adjustable angle for adjusting an air flow rate;
The wafer transfer apparatus wherein the cooling stage is further
equipped with a retainer member and supported on a top face of the
load lock chamber by means of the retainer member.
According to any one of the embodiments specified above, the
cooling chamber is positioned above the load lock chamber and is
therefore able to take in air from the mini environment (a
desirable embodiment is one where a separate cooling means is made
unnecessary by simply utilizing air taken from the mini
environment), consequently achieving low cost, small footprint
and/or small faceprint. In a different embodiment, the cooling
chamber is positioned near the load lock chamber so that wafers can
be transferred between the cooling chamber and load lock chamber
with the transfer robot making no or minimal lateral movements. In
such an embodiment, the cooling chamber also functions as a wafer
stage and can be used as a wafer buffer. In this sense, this
embodiment embodies high throughput.
The above embodiments all relate to a wafer transfer apparatus, but
the present invention is not limited to wafer transfer apparatuses.
Specifically, the present invention also provides semiconductor
manufacturing apparatuses that utilize a wafer transfer apparatus.
According to another embodiment, the present invention provides a
wafer transfer apparatus that comprises: (A) a load lock chamber
connected to a reaction chamber; (B) a wafer cassette that stores
wafers; (C) a mini environment that connects the wafer cassette and
load lock chamber and is equipped with a transfer robot inside; and
(D) a cooling stage positioned near (and preferably above) the load
lock chamber and opening to the mini environment to take in air
from the mini environment; wherein (E) the wafer transfer apparatus
is capable of transferring wafers among the wafer cassette, load
lock chamber and cooling stage by means of the transfer robot.
According to yet another embodiment, the present invention provides
a semiconductor manufacturing apparatus that comprises: (A) a
reaction chamber; (B) a transfer chamber connected to the reaction
chamber; (C) a load lock chamber connected to the transfer chamber;
(D) any one of the foregoing wafer transfer apparatus connected to
the load lock chamber and equipped with the mini environment and
the cooling stage; and (E) a wafer storage part connected to the
wafer transfer apparatus.
The aforementioned embodiments can further include at least the
following embodiments:
The semiconductor manufacturing apparatus wherein the transfer
chamber is positioned below the reaction chamber;
The semiconductor manufacturing apparatus wherein the reaction
chamber and load lock chamber are positioned on an outer periphery
of the transfer chamber.
In the above wafer manufacturing apparatuses and semiconductor
manufacturing apparatuses, a given requirement in one embodiment is
interchangeable with another requirement in a different embodiment,
and individual requirements in different embodiments can also be
combined. The present invention is not limited to the above
embodiments, but it instead encompasses other embodiments that are
able to achieve one or more of the objects described above or other
objects.
The present invention is also applicable to manufacturing methods,
just as it is applicable to wafer transfer apparatuses and
semiconductor manufacturing methods. In yet another embodiment, the
present invention provides a semiconductor manufacturing method
that comprises: a) a step of returning a wafer on which a film has
been formed in the reaction chamber to the load lock chamber; b) a
step of transferring the wafer from the load lock chamber to the
mini environment after the load lock chamber is restored to the
atmospheric pressure, and then to the cooling stage by means of the
transfer robot; c) a step of introducing a next wafer from the
wafer storage part to the mini environment and then to the load
lock chamber by means of the transfer robot; d) a step of
transferring the next wafer from the load lock chamber to the
reaction chamber for formation of film on the wafer; e) a step of
transferring the wafer in the cooling stage to the mini environment
and then to the wafer storage part by means of the transfer robot;
and f) a step of repeating steps a) through e) for each subsequent
wafer. FIG. 8 illustrates an example of the above steps.
In the above embodiment, one wafer is stored in the cooling stage
and transferred. It should be noted, however, that the present
invention is not limited to this design. For example, in yet
another embodiment, the present invention provides a semiconductor
manufacturing method that utilizes one of the aforementioned wafer
transfer apparatuses and is capable of storing two wafers in the
cooling stage; wherein the aforementioned semiconductor
manufacturing method comprises: a) a step of returning a first
wafer on which a film has been formed in the reaction chamber to
the load lock chamber; b) a step of transferring the first wafer
from the load lock chamber to the mini environment after the load
lock chamber is restored to the atmospheric pressure, and then to
the cooling stage by means of the transfer robot; c) a step of
introducing a second wafer from the wafer storage part to the mini
environment and then to the load lock chamber by means of the
transfer robot; d) a step of transferring a second wafer from the
load lock chamber to the reaction chamber for formation of film on
the wafer; e) a step of returning the second wafer on which a film
has been formed in the reaction chamber to the load lock chamber;
f) a step of transferring the second wafer from the load lock
chamber to the mini environment after the load lock chamber is
restored to the atmospheric pressure, and then to the cooling stage
by means of the transfer robot; g) a step of introducing a third
wafer from the wafer storage part to the mini environment and then
to the load lock chamber by means of the transfer robot; h) a step
of transferring the third wafer from the load lock chamber to the
reaction chamber for formation of film on the wafer; i) a step of
transferring the first wafer in the cooling stage to the mini
environment and then to the wafer storage part by means of the
transfer robot; and j) a step of repeating steps e) through i) for
each subsequent wafer. FIG. 9 illustrates an example of the above
steps.
In the above embodiment, two wafers are stored in the cooling stage
and transferred. It should be noted, however, that the present
invention is not limited to this design, and three or more wafers
can also be operated in a similar procedure.
It is also possible to utilize the cooling stage as a wafer stage.
In yet another embodiment, the present invention provides a
semiconductor manufacturing method that utilizes one of the
aforementioned wafer transfer apparatuses and is capable of storing
two wafers in the cooling stage; wherein the aforementioned
semiconductor manufacturing method comprises: a) a step of
introducing an unprocessed wafer from the wafer storage part to the
cooling stage by means of the transfer robot; b) a step of
returning a processed wafer on which a film has been formed in the
reaction chamber to the load lock chamber; c) a step of
transferring the processed wafer from the load lock chamber to the
mini environment after the load lock chamber is restored to the
atmospheric pressure, and then to the cooling stage by means of the
transfer robot; d) a step of transferring the unprocessed wafer
from the cooling stage to the mini environment and then to the load
lock chamber by means of the transfer robot; e) a step of
transferring the unprocessed wafer from the load lock chamber to
the reaction chamber for formation of film on the wafer; f) a step
of introducing a next unprocessed wafer from the wafer storage part
to the cooling stage by means of the transfer robot; g) a step of
transferring the processed wafer in the cooling stage to the mini
environment and then to the wafer storage part by means of the
transfer robot; and h) a step of repeating steps b) through g) for
each subsequent wafer. FIG. 10 illustrates an example of the above
steps.
In one embodiment conforming to any one of the aforementioned
manufacturing methods, the air flow rate on a wafer surface in the
cooling stage is approx. 1 m/s or more.
As explained above, high throughput with a level of stability
sufficient for use in the manufacturing process can be embodied
through utilization of the cooling stage proposed by the present
invention.
In the above explanation, a given requirement in one embodiment is
interchangeable with another requirement in a different embodiment,
and individual requirements in different embodiments can also be
combined. The present invention is not limited to the above
embodiments, but it instead encompasses other embodiments that are
able to achieve one or more of the objects described above or other
objects.
BRIEF DESCRIPTION OF THE DRAWINGS
The present invention is further explained below with reference to
drawings. It should be noted, however, that the present invention
is not limited to these drawings. It should also be noted that the
drawings are oversimplified for illustrative purposes.
FIG. 1 is a schematic diagram showing a CVD film formation
apparatus with a cooling stage according to an embodiment of the
present invention.
FIG. 2 is a partial section view showing the structure of and
around a mini environment with a cooling stage as well as flows of
air inside the mini environment according to an embodiment of the
present invention.
FIG. 3 is a plan section view showing one example of CVD film
forming apparatus to which a cooling stage can be installed
according to an embodiment of the present invention.
FIG. 4A is a plan section view showing the structure of a cooling
stage with a variable louver according to an embodiment of the
present invention. FIG. 4B is a side view of the cooling stage in
an installed state.
FIG. 5A is a plan section view showing the structure of a cooling
stage with retainer grooves according to an embodiment of the
present invention. FIG. 5B is a rear view of the same structure
(the cooling stage on the right has no retainer grooves), while
FIG. 5C is a side view showing the same structure.
FIG. 6A is a side view showing the structure of a cooling stage
with gate valves according to an embodiment of the present
invention, while FIG. 6B is a plan view of the same structure.
FIGS. 7A, 7B and 7C show an example of a variable louver used in a
cooling stage according to an embodiment of the present invention.
FIG. 7A shows the variable louver in a fully open state, FIG. 7B
shows the variable louver in a partially open state, and FIG. 7C
shows the variable louver in a fully closed state.
FIG. 8 shows a wafer transfer sequence involving a cooling stage
for storing one wafer according to an embodiment of the present
invention.
FIG. 9 shows a wafer transfer sequence involving a cooling stage
capable of storing two wafers according to an embodiment of the
present invention.
FIG. 10 shows another wafer transfer sequence involving a cooling
stage capable of storing two wafers according to an embodiment of
the present invention.
FIG. 11 is a section view showing a cluster CVD film formation
apparatus to which a cooling stage can be installed according to an
embodiment of the present invention.
FIG. 12 is a graph showing the trend of wafer temperature in an
example of the present invention.
Explanation of the symbols: 1: Upper lifter, 2: Gas box, 3: Utility
box, 4: Touch screen, 5: Radical cleaning unit, 6: Matching box, 7:
Reaction chamber, 8: I/O load lock chamber, 9: Pump for I/O
chamber, 10: FOUP opener, 11: FOUP, 12: Mini environment, 13:
Signal tower, 14: Fan filter unit, 15: Cooling stage, 20:
Pre-filter, 21: Fan, 22: ULPA filter, 23: Buffer plate, 24: FE
robot, 25: Adjustable dampers, 40: Set plate, 41: Wafer, 42:
Adjustable louver, 43: Cooling-stage retainer plate, 50: Retainer
groove, 51: 10C gate valve, 60: Front gate valve, 61: Gate-valve
open/close air cylinder, 62: Gate-valve open/close air cylinder,
63: Rear gate valve, 71: Variable louver guide, 72: Variable louver
screw, 73: Variable louver hole, 110: Load lock chamber, 111:
Transfer chamber, 112: Vacuum robot
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Embodiments of the present invention are explained below by
referring to the drawings. It should be noted, however, that the
present invention is not limited to these drawings and
embodiments.
As mentioned above, the invention pertaining to the present
application for patent encompasses various embodiments and can be
used widely in CVD film formation apparatuses. FIG. 1 shows a CVD
film formation apparatus with cooling stage according to an
embodiment of the present invention. This embodiment is a
semiconductor manufacturing apparatus of the vacuum-load-lock type,
comprising a transfer chamber and a reaction chamber (normally a
transfer chamber is positioned below a reaction chamber, and both
chambers together are referred to as a reaction chamber) 7, a mini
environment 12, and a load lock chamber 8 connecting the reaction
chamber 7 and the mini environment 12, wherein the mini environment
12 is equipped with a transfer robot (atmospheric pressure robot)
24 (see FIG. 3) so that wafers can be transferred between the
transfer robot 24 and various chambers. The mini environment 12 is
also connected to an FOUP (Front Opening Unified Pod; a general
wafer cassette that stores 300-mm wafers) 11 so that wafers can be
transferred between the FOUP 11 and load lock chamber 8 by means of
the transfer robot 24. In this embodiment, the mini environment 12
refers to a clean environment having an FFU (Fan Filter Unit) 14 on
top. The FOUP 11 may be a simple wafer cassette (the storable
wafers need not be 300 mm in size).
As for other parts of the structure, an FOUP opener 10 that opens
and closes the FOUP 11 is provided underneath the FOUP, while a
signal tower 13 is positioned on a side face of the FFU 14 to
indicate the condition of the apparatus. For example, this signal
tower can be designed in such a way that a red lamp will turn on if
an alarm occurs (apparatus failure), a blue lamp will be lit while
the apparatus is standing by prior to lot processing, a yellow lamp
will turn on when lot processing is completed, a green lamp will be
lit while lot processing is in progress, and so on. Located above
the reaction chamber 7 is a matching box 6 that adjusts the
impedance by applying RF power to the reaction chamber. A radical
cleaning unit 5, which is a remote plasma chamber, is also provided
to clean the interior of the reaction chamber (RC) 7. On top of the
radical cleaning unit 5, there are a gas box 2 and a utility box 3.
In addition, an upper lifter 1 is provided so that the shower head
can be suspended at the upper lifter during RC maintenance to be
moved in the forward or backward direction in accordance with the
location that requires servicing. A touch screen 4 for controlling
the CVD apparatus is provided on the front side of the apparatus.
The above is only one example and the present invention is not
limited to this structure.
In the above embodiment, a cooling stage 15 is installed above
(directly above, in this example) the load lock chamber 8 so that
air in the mini environment 12 can be taken in to cool the
wafers.
FIG. 2 is a partial section view showing the structure of and
around a mini environment (M/E) 12 with cooling stage as well as
flows of air inside the mini environment according to an embodiment
of the present invention. The fan filter unit above the M/E 12
comprises a sirocco fan 21 and a ULPA filter 22 and is designed to
take in air from the top of the FFU via a pre-filter 20. The air is
cleaned via the ULPA filter, and then supplied into the M/E via a
buffer plate 23. Adjustable louvers (dampers) 25 are installed
below the M/E 12 to exhaust air and adjust the pressure inside the
M/E 12. In other words, air is constantly flowing from top to
bottom inside the MIE 12.
One example of the environment of this M/E 12 is given below.
Temperature (=room temperature): Approx. 25.degree. C.
(alternatively, no temperature adjustment)
Air velocity: Approx. 0.5 m/s.+-.0.1 m/s (in one embodiment,
between approx. 0.1 m/s and approx. 1.5 m/s, preferably between
approx. 0.3 m/s and approx. 1.0 r/s)
Air volume: Approx. 16 m.sup.3/m.+-.3 m.sup.3/m
Pressure: Approx. 4.0 Pa.+-.0.8 Pa (in one embodiment, between
approx. 2 Pa and approx. 8 Pa (gauge pressure))
The above ranges, especially the range of air volume, will vary
depending on the volume of the M/E. These values can also be
adjusted by means of the variable louvers 25 in order to adjust the
wafer cooling capacity.
In this embodiment, a cooling stage 15 is positioned above the load
lock chamber 8 and opened to the M/E 12 so that air inside the M/E
is take into the cooling stage 15. Air can be taken into the
cooling stage because the pressure inside the M/E is higher than
the outside air pressure (no separate air blower or similar device
is required). This cooling stage 15 can store two wafers on top of
each other, but the present invention is not limited to this
design.
After a film is formed on a wafer inside the reaction chamber, the
wafer is returned to the load lock chamber, after which the load
lock chamber is restored to the atmospheric pressure and then the
wafer is returned to the FOUP. Since the wafer temperature is still
around 200.degree. C. immediately after the load lock chamber has
been restored to the atmospheric pressure, the wafer cannot be
returned to the FOUP right away. In this embodiment, the wafer is
placed in the cooling stage 15 first and held there for a while so
that another wafer can be transferred from the FOUP into the load
lock chamber. The transfer sequence involving the cooling stage
will be explained later.
An example of the temperature and velocity of air entering the
cooling stage 15 from the M/E 12 (air passing over the wafer stored
in the M/E; i.e., cooling stage environment) is given below.
Temperature (near the outlet): Approx. 60.degree. C..+-.10.degree.
C. (in one embodiment, between approx. 40.degree. C. and approx.
80.degree. C.)
Air velocity: Approx. 1.7 m/s.+-.0.4 m/s (in one embodiment,
between approx. 1 m/s and approx. 5 m/s) (1.5 to 6 times, or
preferably 2 times to 4 times the air velocity in the M/E)
The outlet temperature will vary depending on the temperature of
the wafer at the time the wafer is stored into the cooling stage.
Once the wafer is stored in the cooling stage 15, heat is
efficiently removed from the surface of the wafer by means of clean
air flowing over the wafer surface.
As explained above, providing a cooling stage improves the wafer
processing capacity and increases the throughput. The reasons are
considered as follows (it should be noted that the present
invention is not limited to those accounted for by these reasons).
In one embodiment, for example, air may be forcibly supplied to the
wafer surface, which improves the heat transfer efficiency on the
wafer surface and shortens the cooling time itself. Also, the
transfer speed does not have to be limited. Specifically, it takes
a shorter time to transfer a wafer to the cooling stage located,
for example, immediately above the load lock chamber after film has
been formed on the wafer, than to return the wafer directly to the
FOUP (wafer cassette). Furthermore, after elapse of a specified
time (such as 60 seconds), the wafer stored in the cooling stage
can be returned to the FOUP (cassette) whenever the robot is idle.
This prevents the transfer speed from being limited. The steps to
prevent the transfer speed from being limited will be explained
later.
Next, the structures of cooling stages in some embodiments are
explained. It should be noted, however, that the present invention
is not limited to these embodiments.
FIG. 4A is a plan section view showing the structure of a cooling
stage (capable of storing two wafers) with a variable louver
according to an embodiment of the present invention. FIG. 4B is a
side view of aforementioned cooling stage in an installed state. In
this embodiment, the cooling stage 15 is secured on the load lock
chamber 8 using a cooling-stage retainer plate 43. Also, the
connection port on the side wall of the M/E 12 to which the cooling
stage 15 is connected is sealed with foamed sponge (EPDM). The
cooling stage 15 need not be positioned directly above the load
lock chamber 8. However, it should ideally be located near the gate
valve on the load lock chamber 8 so that wafers can be transferred
between the chambers with the minimum movements of the transfer
robot. A layout in which the cooling stage 15 is positioned
directly above the load lock chamber 8, where the gate valve on the
load lock chamber 8 and the opening in (connection port on) the
cooling stage 15 are aligned with the rotating axis (vertical axis)
of the transfer robot, is preferred because wafers can be
transferred between the load lock chamber 8 and cooling stage 15
with only the vertical movements of the transfer robot and thus the
transfer time can be reduced.
The cooling stage 15 can be made of plastics offering transparency
and heat resistance (one example is polycarbonate whose thermal
deformation temperature is 137.degree. C. to 142.degree. C.).
However, the material is not limited to plastics, and aluminum and
other metals may be used to construct the cooling stage. The size
of the cooling stage 15 should be such that a wafer 41 will not
contact the interior walls of the cooling stage as it is
transferred into and out of the cooling stage. Desirably, the
volume of the cooling stage should be minimized. For example, in a
cooling stage 15 that stores one or two wafers, the size of the
connection port on (opening in) the M/E 12 may be adjusted to a
level equivalent to the gate valve on the load lock chamber. A set
plate 40 is attached inside the cooling stage 15 to support wafers.
This set plate 40 can be made of aluminum (A6061), for example.
It is desirable that the air outlet of the cooling stage be made
smaller than the connection port (air inlet) on the M/E 12. By this
way, the air velocity on the wafer surface can be improved
efficiently. In the embodiment illustrated by FIGS. 4A and 4B, a
variable louver 42 is installed at the air outlet in such a way
that its angle can be adjusted. The air velocity (cooling speed)
can be adjusted by means of adjusting the louver angle.
FIGS. 7A, 7B and 7C show an example of cooling stage (capable of
storing two wafers) with a variable louver. The variable louver 42
is secured to the cooling stage using two variable louver screws 72
via a variable louver guide 71. Variable louver holes 73 are
provided in the variable louver 42 and the variable louver screws
72 are inserted into these holes to secure the variable louver.
Since the variable louver holes 73 in the variable louver 42 are
longer than they are wide, these holes can be used to adjust the
vertical position of the variable louver. The variable louver 42
and variable louver guide 71 (or the air outlet surface of the
cooling stage) each have a slit. By moving the variable louver
vertically, the overlap of the slits can be adjusted to change the
louver angle. FIG. 7A shows the variable louver 42 in a fully open
state, FIG. 7B shows the variable louver in a partially open state,
and FIG. 7C shows the variable louver in a fully closed state.
The variable louver need not be provided. FIG. 5A is a plan section
view showing the structure of a cooling stage (capable of storing
two wafers) with retainer grooves according to an embodiment of the
present invention. FIG. 5B is a rear view of the same structure
(the cooling stage on the right has no retainer grooves), while
FIG. 5C is a side view showing the same structure. In this
embodiment, two levels of retainer grooves 50 are provided at the
air outlet. FIG. 5B also illustrates a position relationship with
respect to the gate valve 51 on the load lock chamber.
Normally, the opening area of the connection port (air inlet) is
larger than the opening area of the air outlet. However, the area
ratio is not limited to a specific value and should be adjusted to
an appropriate level at which the air velocity can be achieved on
the wafer surface. In one embodiment, the opening area ratios may
be adjusted to a range of approx. 2:1 to approx. 50:1, or
preferably to a range of approx. 10:1 to approx. 30:1.
It is also possible to install a gate valve at the air outlet. FIG.
6A is a side view showing the structure of a cooling stage (capable
of storing two wafers) with gate valves according to an embodiment
of the present invention, while FIG. 6B is a plan view of the same
structure. A front gate valve 60 and a gate-valve open/close air
cylinder 61 that opens and closes the front gate valve are provided
on the connection port side, while a rear gate valve 63 and a
gate-valve open/close air cylinder 62 that opens and closes the
rear gate valve are installed on the air outlet side. The gate
valves remain "open" in a normal condition. If the FFU shuts down
due to power outage, etc., the gate valves will close to protect
the wafers from contaminated air that may otherwise come in contact
with the wafers during the period of non-operation of the FFU.
The top face of the cooling stage should ideally be inclined from
the air inlet toward the outlet. This way, the air velocity rises
toward the air outlet. Although the angle of inclination should be
selected as deemed appropriate in accordance with the size of wafer
and the specified area ratio of inlet and outlet openings, in one
embodiment the angle of inclination may be adjusted to a range of
approx. 2.degree. to approx. 20.degree., or preferably to a range
of approx. 5.degree. to approx. 10.degree..
The cooling stage may have only one level or it can have two or
more levels. A desired number of wafers stored in the cooling stage
can be selected in accordance with the film formation time. In
other words, the cooling stage may need to store only one wafer if
the film formation time is long (since the cooling effect takes
place while film is being formed, there is no need to use the
cooling stage as a buffer). If the film formation time is short,
however, preferably the cooling stage should be able to store two,
three or more wafers and the cooling stage should be used as a
buffer. In short, a desired number of wafers can be selected as
long as the transfer speed is not limited. Normally, the number of
wafers stored in the cooling stage increases as the number of
wafers stored in the load lock chamber increases. It is also
possible to provide one cooling stage for two or more load lock
chamber, in which case it is desirable that the cooling stage be
able to store multiple wafers. When multiple wafers are stored in
the cooling stage, these wafers may be arranged on top of one
another or side by side. Since the air volume is relatively large,
the number of wafers stored in the cooling stage has minimal impact
on the cooling time.
In one embodiment, the target cooling time may be set so that
approx. 60 seconds (in an embodiment, 30 seconds, 50 seconds, 70
seconds, 90 seconds, 120 seconds, or any other duration in between)
will be required to reduce the wafer temperature to 100.degree. C.
or below. If the target cooling time is approx. 60 seconds, it
means the cooling time per wafer is 30 seconds if two wafers are
stored, or 60 seconds if only one wafer is stored.
Cooling wafers is not the only purpose of the cooling stage. The
cooling stage can also be used simply as a wafer stage on which
wafers are placed. For example, only one wafer may need to be
placed in the cooling stage when the film formation time is long
(the transfer speed is not limited). In this case, the upper stage
(if the cooling stage can store two wafers) can be used as a wafer
stage. Specifically, after the robot has transferred a wafer from
the FOUP to the load lock chamber, the remaining time can be used
to transfer the next wafer from the FOUP to the wafer stage in
advance. This way, the time required to exchange wafers in the load
lock chamber can be reduced. For example, the time required by the
robot to access the; FOUP to take a wafer can be reduced in this
embodiment, because after the robot returns a wafer on which film
has been formed from the load lock chamber to the cooling chamber,
it only needs to take a pre-placed wafer from the wafer stage
directly above and place it into the load lock chamber. This
switching of cooling stage function from "cooling stage" to "wafer
stage" can be implemented by software with ease.
The cooling stage may be installed on a general cluster tool, as
shown in FIG. 11. This cluster tool has multiple reaction chambers
7 and multiple load lock chambers 110 around a transfer chamber 7.
A vacuum robot 112 is provided inside the transfer chamber 111 so
that wafers can be transferred among the chambers. In this case, it
is desirable that the cooling stage be positioned above the load
lock chambers 110.
As explained earlier, one embodiment can be considered that adopts
a structure whereby clean air is introduced to the M/E from an AFE
(Atmospheric Front End), passed through the cooling stage provided
above the load lock chamber, and then exhausted to the apparatus
side, and wafers are set along this air channel for cooling. The
cooling stage may be provided below the load lock chamber. If the
cooling stage is provided below the load lock chamber, the air
intake efficiency will drop, but it will become possible to select
an appropriate cooling stage position in accordance with the
apparatus and its environment. Additionally, it is also be possible
to install the cooling stage not on the same surface as the gate
valve on the load lock chamber, but on a facing surface or adjacent
surface. In this case, however, the transfer efficiency may be
compromised.
Next, examples of different transfer sequences, each involving a
cooling stage, are explained.
FIG. 8 shows a wafer transfer sequence involving a cooling stage
for storing one wafer as proposed in one embodiment. To be
specific, this sequence presents a semiconductor manufacturing
method that includes the following steps (the numbers in the figure
correspond to the step numbers):
a) a step of returning a wafer W1 on which a film has been formed
in the reaction chamber 7 to the load lock chamber 8;
b) a step of transferring the wafer W1 from the load lock chamber 8
to the mini environment 12 after the load lock chamber 8 is
restored to the atmospheric pressure, then to the cooling stage 15
by means of a transfer robot (not illustrated);
c) a step of introducing a next wafer W2 from the wafer storage
part 11 to the mini environment 12 and then to the load lock
chamber 8 by means of the transfer robot;
d) a step of transferring the wafer W2 from the load lock chamber 8
to the reaction chamber 7 for formation of film on the wafer;
e) a step of transferring the wafer W1 in the cooling stage 15 to
the mini-environment 12 and then to the wafer storage part 11 by
means of the transfer robot; and
f) a step of repeating steps a) through e) for each subsequent
wafer.
FIG. 9 shows a wafer transfer sequence involving a cooling stage
capable of storing two wafers as proposed in another embodiment. To
be specific, this sequence presents a semiconductor manufacturing
method that includes the following steps (the numbers in the figure
correspond to the step numbers):
a) a step of returning a wafer W1 on which a film has been formed
in the reaction chamber 7 to the load lock chamber 8;
b) a step of transferring the wafer W1 from the load lock chamber 8
to the mini environment 12 after the load lock chamber 8 is
restored to the atmospheric pressure, and then to the cooling stage
15 by means of a transfer robot (not illustrated);
c) a step of introducing a next wafer W2 from the wafer storage
part 11 to the mini environment 12 and then to the load lock
chamber 8 by means of the transfer robot;
d) a step of transferring the wafer W2 from the load lock chamber 8
to the reaction chamber 7 for formation of film on the wafer;
e) a step of returning the wafer W2 on which a film has been formed
in the reaction chamber 7 to the load lock chamber 8;
f) a step of transferring the wafer W2 from the load lock chamber 8
to the mini environment 12 after the load lock chamber 8 is
restored to the atmospheric pressure, and then to the cooling stage
15 by means of the transfer robot;
g) a step of introducing a next wafer W3 from the wafer storage
part 11 to the mini environment 12 and then to the load lock
chamber 8 by means of the transfer robot;
h) a step of transferring the wafer W3 from the load lock chamber 8
to the reaction chamber 7 for formation of film on the wafer;
i) a step of transferring the wafer W1 in the cooling stage 15 to
the mini environment 12 and then to the wafer storage part 11 by
means of the transfer robot; and
j) a step of repeating steps e) through i) for each subsequent
wafer.
FIG. 10 shows a wafer transfer sequence involving a cooling stage
capable of storing two wafers as proposed in another embodiment. To
be specific, this sequence presents a semiconductor manufacturing
method that includes the following steps (the numbers in the figure
correspond to the step numbers):
a) a step of introducing an unprocessed wafer W2 from the wafer
storage part 11 to the cooling stage 15 by means of a transfer
robot (not illustrated);
b) a step of returning a processed wafer W1 on which a film has
been formed in the reaction chamber 7 to the load lock chamber
8;
c) a step of transferring the processed wafer W1 from the load lock
chamber 8 to the mini environment 12 after the load lock chamber 8
is restored to the atmospheric pressure, and then to the cooling
stage 15 by means of the transfer robot;
d) a step of transferring the unprocessed wafer W2 from the cooling
stage 15 to the mini environment 12 and to the load lock chamber 8
by means of the transfer robot;
e) a step of transferring the unprocessed wafer W2 from the load
lock chamber 8 to the reaction chamber 7 for formation of film on
the wafer;
f) a step of introducing a next unprocessed wafer W3 from the wafer
storage part 11 to the cooling stage 15 by means of the transfer
robot;
g) a step of transferring the processed wafer W1 in the cooling
stage 815 to the mini environment 12 and to the wafer storage part
11 by means of the transfer robot; and
h) a step of repeating steps b) through g) for each subsequent
wafer.
As explained above, using a cooling stage improves the wafer
processing capacity and increases the throughput. The reasons are
considered as follows (it should be noted that the, present
invention is not limited to those accounted for by these reasons).
In one embodiment, for example, air may be forcibly supplied to the
wafer surface, which improves the heat transfer efficiency on the
wafer surface and shortens the cooling time itself. Also, the
transfer speed does not have to be limited. Specifically, it takes
a shorter time to transfer a wafer to the cooling stage located,
for example, immediately above the load lock chamber after film has
been formed on the wafer, than to return the wafer directly to the
FOUP (wafer cassette). Furthermore, after elapse of a specified
time (such as 60 seconds), the wafer stored in the cooling stage
can be returned to the FOUP (cassette) whenever the robot is idle.
This prevents the transfer speed from being limited.
Next, an example of wafer cooling based on the present invention
(by using the cooling stage shown in FIGS. 5A and 5B) is given.
FIG. 12 is a graph showing the trend of wafer temperature in this
example. Temperature was measured using a thermocouple (TC)
attached near the set plate inside the cooling stage. When a wafer
is transferred and placed on the set plate, the back surface of the
wafer contacts the TC so that the TC can measure the wafer
temperature. This graph starts from "48:11.0." This is the time
recorded on the data logger when measurement was started and has no
meaning as an absolute value (the time axis of this graph provides
a relative scale).
M/E environment:
Temperature (=room temperature): Approx. 25.degree. C.
Air velocity: Approx. 0.5 m/s
Air volume: Approx. 16 m.sup.3/m
Pressure: Approx. 4.0 Pa
Cooling stage environment:
Temperature (near the outlet): Approx. 60.degree. C.
Air velocity: Approx. 1.7 m/s
As shown in the graph, at the moment the first wafer was placed in
the cooling stage, the TC temperature near the set plate increased
and exceeded 200.degree. C. Thereafter, the temperature dropped to
100.degree. C. or below within approx. 60 seconds and the wafer was
transferred out of the cooling stage. Thereafter, as the next
processed wafer approached the TC near the set plate, the heat of
the wafer caused the temperature to increase slightly (50:17
point), and at the moment the aforementioned wafer was placed in
the cooling stage, the TC temperature near the set plate increased
and exceeded 200.degree. C. Thereafter, the temperature dropped to
100.degree. C. or below within approx. 60 seconds and the wafer was
transferred out of the cooling stage. Herein, "put" in the graph
indicates a point at which a wafer was physically placed on the set
plate and the back surface of the wafer contacted the TC, while
"get" indicates a point at which a wafer was physically removed
from the set plate and the back surface of the wafer separated from
the TC. Therefore, each wafer-cooling curve corresponds to the
section between the "max" temperature and "get" temperature.
As shown, according to this example wafers can be cooled
efficiently as they are transferred in and out.
Furthermore, as explained above, according to at least one
embodiment, the present invention can realize an apparatus and
method offering low cost, small footprint, small faceprint and high
throughput, and also can realize a semiconductor manufacturing
apparatus that embodies high throughput with a level of stability
sufficient for use in the manufacturing process.
* * * * *